The present disclosure relates to a semiconductor device, and can be suitably used, for example, for a semiconductor device that generates a signal to control a device used in a time-synchronized distributed system.
In a distributed system including a plurality of elements (nodes) connected to a network, each of the plurality of nodes operates based on its local clock. In some implementations, in order to accomplish synchronization of events occurring in the plurality of nodes, for example, the distributed system may need to time-synchronize the plurality of nodes (i.e., their local clocks). The time synchronization of the distributed system is accomplished by frequently exchanging messages (information) among the plurality of nodes in the distributed system. Typically, any one of the nodes in the distributed system that is predetermined or dynamically selected serves as a master clock node. The local clock of the master clock node is called a master clock. The master clock node exchanges messages (information) with other nodes (slave clock nodes) in the distributed system and thus each slave clock node synchronizes its local clock (i.e., slave clock) with the master clock.
Precision Time Protocol (PTP), which is defined in IEEE Standard 1588, is one of the representative examples of a time synchronization method of the distributed system. Further, generalized PTP (gPTP) defined in IEEE Standard 802.1AS, which is one of the standards that constitute Ethernet Audio/Video Bridging (AVB), is known as a time synchronization method using the PTP. The gPTP defines a time synchronization method in IEEE 802.3 network (i.e., Wired LAN) and IEEE 802.11 network (i.e., Wireless LAN). In the PTP, the master clock node is called a ground master clock and the slave clock node is called a clock slave. In order to accurately synchronize with the ground master clock, the clock slave exchanges messages (i.e., Sync, Follow_Up, Delay_Request, and Delay_Response) with the ground master clock, calculates network delay time based on the transmission time and the reception time of these messages, and adjusts its local clock using the calculated network delay time.
The distributed system that requires the time synchronization is, for example, a manufacturing system including an industrial robot and a metrology device therefor, a surveillance system including networked surveillance cameras, and an automotive camera system. The automotive camera system includes a surround view camera system, a bird view camera system, and a side view camera system. This automotive camera system uses a plurality of cameras and processes images taken by the plurality of cameras to assist parking, detect obstacles and the like.
Japanese Patent Application Publication No. 2005-286453 discloses a technique for synchronizing in time a plurality of cameras, each connected to a network, using a synchronization procedure similar to the PTP.